Method of making toothed racks

ABSTRACT

The flame of a cutting torch is passed through a central longitudinal zone of an elongated blank so that the kerf forms two rack sections with substantially identical teeth thereon. Rack sections with such flame cut teeth are secured together in side-by-side relationship, with their teeth in endwise register, to form a rack exceeding the thickness of the blanks from which the rack sections are cut. Before flame cutting of the teeth is commenced, thin slices are flame cut from opposite faces of the blank which are to become the backs of the rack sections, to prevent warping of the flame cut rack sections along their lengths.

United States Patent [1 1 Maxon, Jr. et a1.

[451 Jan. 23, 1973 METHOD OF MAKING TOOTHED RACKS [76] inventors:Glenway Maxon, Jr.; William H. B. Wright, 111, both of 3129 West MillRoad, Milwaukee, Wis. 53209 [22] Filed: Aug. 5, 1971 [211 App]. No.:169,221

Related US. Application Data [62] Division of Ser. No. 17,126, March 6,1970.

[52] US. Cl. ..29/l59.2, 29/4l2, 74/422 [51] Int. Cl. ..B2ld 53/28, B2lh5/00, B2lk l/30, 1323p 15/14, B29d 15/00 [58] Field of Search..29/l59.2,159 R,412,415,

29/416; 266/23 K, 23 E, 23 R; 74/422, 30, 89.11, 29; 90/1, 2; 148/9 [56]References Cited UNITED STATES PATENTS Brinton ..29/159.2

Wigley ..29/l59.2

2,432,161 12/1947 Johnston ..266/23 K X 3,306,597 2/1967 Maxon, Jr. etal. "266/23 K FOREIGN PATENTS OR APPLICATIONS 257,938 1/1927 GreatBritain ..29/1592 Primary Examiner-Charles W. Lanham AssistantExaminerVictor A. DiPalma Attorneylra Milton Jones [57] ABSTRACT Theflame of a cutting torch is passed through a central longitudinal zoneof an elongated blank so that the kerf forms two rack sections withsubstantially identical teeth thereon. Rack sections with such flame cutteeth are secured together in side-by-side relationship, with theirteeth in endwise register, to form a rack exceeding the thickness of theblanks from which the rack sections are cut. Before flame cutting of theteeth is commenced, thin slices are flame cut from opposite faces of theblank which are to become the backs of the rack sections, to preventwarping of the flame cut rack sections along their lengths.

9 Claims, 5 Drawing Figures PATENTEDJAH23 I975 3.711.915

SHEET 1 [IF 2 PATENTEUJAH 23 1915 SHEET 2 [IF 2 METHOD OF MAKINGTOOTIIED RACKS This application is a division of our copendingapplication, Ser. No. 17,126, filed Mar. 6, 1970.

Like our application Ser. No. 843,725, filed July 22, 1969 nowabandoned, of which said application, Ser. No. 17,126, is acontinuation-in-part, this invention relates to an improved method ofmaking racks.

In a more specific sense, this invention is concerned with the flamecutting of racks having substantial face width and large size teeth,while achieving an accuracy that was hitherto unheard of.

It is generally recognized that large size racks can be flame cut at farless cost than is entailed when the conventional casting and machiningpractices are resorted to. However, because the attainment of asubstantial degree of accuracy in the flame cutting of teeth in blanksof the thickness required for racks of substantial face width washeretofore considered impossible, that technique was employed only whenaccuracy of the rack teeth, both as to profile and pitch, was not aprerequisite.

It has now been discovered that two of the main reasons for the abovementioned deficiency of the flame cutting technique were distortion ofthe flame of the torch, especially when cutting the tooth tips androots, and thermal expansion of the blank during the flame cuttingoperation.

The blank will expand to an extent depending upon the increase in thetemperature of the metal adjoining the cut therein; and bearing in mindthat the velocity of cutting must be decreased and the diameter of thetorch flame must be increased to cut through the thicker blanks, thetemperature of the metal will rise as a function of the thickness of theblanks being cut.

Consequently, excessive heat is generated in the interiors ofsubstantially thick blanks during flame cutting of teeth therein, whichheat cannot be dis sipated sufficiently to enable thermal expansion tobe controlled, even though quenching is resorted to by directing jets ofcooling water onto the flame cut areas as soon as possible after theyhave been acted upon by the torch.

With the above in mind, it is an object of this invention to provide amethod of making racks of any desired face width from laminationscomprised of substantially identical rack sections, matching pairs ofwhich can be simultaneously flame cut from single blanks having athickness less than the finished rack, and thin enough to enable thermalexpansion thereof to be readily controlled and to minimize deviation oftooth profile due to flame distortion.

Another object of the invention is to provide a method of making racksaccording to the manner described in the preceding object, which methodsubstantially eliminates lengthwise warping of the flame cut racksections.

With these objects in mind, the invention resides in the novel methodsubstantially as hereinafter described and more particularly defined bythe appended claims. This disclosure, however, is intended merely toexemplify the invention, the nature of which is defined by the appendedclaims.

The accompanying drawings illustrate one complete example of the methodaccording to the best mode so far devised for practical application ofthe principles thereof, and in which:

FIGS. 1 and 2 are fragmentary perspective views illustrating how racksare made in accordance with this invention;

FIG. 3 is a more or less diagrammatic plan view of a pair of matchingrack sections illustrating in somewhat exaggerated form how the sectionstend to warp along their length;

FIG. 4 is a view similar to FIG. 3, showing how straight rack sectionscan be cut in accordance with the method of this invention; and

FIG. 5 is a perspective view illustrating that thin slices of the blankare cut from opposite longitudinal edges thereof before flame cutting ofthe rack teeth is commenced, to assure against warping of the sections.

Referring now to the accompanying drawings, FIGS. 1 and 2 disclose howracks, with a simple form of tooth, can be flame cut in accordance withthe method of this invention, from blanks having a rectangular crosssection. As best seen in FIG. 1, the flame of a cutting torch 12 isdirected downwardly through a central longitudinal zone 13 of the blank14, to produce a kerf that is preferably but not necessarily parallel tothe opposite narrow sides of the blank and defines equispaced teeth 15therein with the teeth extending in a row lengthwise of the blank. Withrespect to the rectangular cross section of the blank, the flame of thetorch is passed through the thickness of the blank, from one wide sideof the rectangle to the other.

The teeth 15 are cut so as to be identical to one another, with straightsides, tips and roots. Accurate cutting of the teeth depends to a largedegree on the care with which relative motion between the torch and theblank is effected, and it should be carried out in a way that assuresthat the speed of the torch relative to the surface of the blank beingcut is such as to maintain a smooth, uniform kerf.

The cutting of rack teeth in the central longitudinal zone of the blankproduces two rack sections 16 and 17, with identical meshing teeth 15thereon. Flame cutting is preferably commenced at one end of the blankin a way to define one-half a tooth 15 on said end of one rack section16, and one-half a tooth space on the laterally adjacent rack section17, as seen in FIG. 1; and with the blank free to expand lengthwisetoward said one end as it is heated by the torch but held againstthermal expansion in the opposite direction. The aforesaid copendingapplication, Ser. No. 17,126, which discloses a machine for flamecutting racks, can be consulted for a disclosure of one means ofconfining the blank against thermal expansion in the direction towardits end opposite the one at which the cut is started.

It is also advantageous, though not essential, to effect flame cuttingthrough a longitudinal zone of the blank which is at its exact center,so that flame cutting takes place at an average equal distance from theopposite longitudinal edges of the blank. With reference to therectangular cross section of the blank, flame cutting is performed alonga longitudinal zone of the blank midway between the ends of therectangle. Such flame cutting will produce two rack sections which areidentical except that their teeth are offset from one another a distanceequal to one-half of the spacing or pitch of the rack teeth.

After the torch has cut teeth in the blank along its entire length, thetwo rack sections 16 and 17 are separated and laid one against the otheras seen in FIG. 2, with the sections so oriented that all of their teethface in the same direction, and one section is offset lengthwise fromthe other by one-half of a tooth space so as to dispose the teeth of thetwo sections in exact endwise register. Preferably the rack section 17is disposed'with the first full tooth 15 cut thereon in endwise registerwith the first full tooth cut on the section 16, and with thosesides ofthe sections that correspond to the face of the blank at which the flameof the torch entered it in mating engagement with one another. The faceof the blank referred to is uppermost in FIG. 1, in

designate the flame-entering face of the blank. The arrows 16' and 17 inFIG. 2 show how the blank section 17 was turned up and over the racksection16, and then disposed with its teeth in register with those on,the latter section.

After the rack sections 16 and 17 are laid one against the other andoriented as seen in FIG. 2, they can be secured together in any desiredway as for instance by bolts, welding or even by an epoxy bonding agent.Usually, any frictional teeth on the ends of the rack sections arecutoff to leave both ends of the sections flush with one another andsimilar in appearance to the end of section 17 seen in FIG. 2.

One of the main features of the method described, is that the securementof the two rack sections 16 and 17 together with their teeth in endwiseregister produces a rack having a width equal to twice the thickness ofthe blank from which the rack was cut. a

From the above it will also be apparentthat if the proper care isexercised during the flame cutting operation, no machining, other thandescaling and deburring, should be necessary on the flanks or tips ofthe rack teeth; and a number of .rack units laminated in the mannerdescribed can be secured to a supporting surface in end to end relationto provide a rack of any desired length and at far less cost that wouldbe entailed if more conventional machining operations had been employed.I

The act of flame cutting of the matching rack sections may have atendency to produce lengthwise warping thereof, as seen in exaggeratedform in FIG. 3. Such lengthwise warping causes the toothed edges of thesections to assume a concave curvature while the backs of the sectionstake on a-convex curvature.

Lengthwise warping of the rack sections can be controlled andsubstantially completely eliminated in accordance with this invention bya flame cutting operation performed on the blank before the teeth .are'flame cut therein, and which involves cutting off thin slices from thosefaces of the blank which are to become the backs of the rack sections.FIG. shows one such slice 18 which has already been flame cut from oneface of the blank, with the torch in the act of cutting a similar slice18 from the opposite face of the blank. Obviously,

' both cuts can be made simultaneously. The outlines of the rack teethto be thereafter cut in the portion of the blank medially between saidfaces thereof are shown in construction lines.

We are unable to explain exactly why the flame cutting of thin slicesfrom opposite sides of the blank in the manner described above minimizeslengthwise warping of the matching rack sections.

' which arrows 16' and 17' on the two rack sections It should beapparent that racks can be flame cut with teeth having rounded tips andgullets of corresponding concavity at the roots of the teeth, forgreater strength; and that the teeth may have cycloidal or straightflanks and faces that are either symmetrical or non-symmetrical. Withany non-symmetrical tooth form, however, the racks should be flame cutso that the sections from which they are laminated can be oriented inone way or another to bring their teeth into the end to end matching orcongruent relationship in which they complement one another to severallyor collectively provide the teeth of the finished rack.

Persons skilled in the art will also appreciate that the above describedmethod also makes possible the production of flame cut racks having aface width greater than twice the thickness of the blank from which theracks are cut. This of course will require the cutting of the same styleand size of teeth in each of two or more blanks, one blank at a time.

'There may also betimes when it may be necessary to desirable to effectflame cutting along one marginal edge portion of a blank. At such times,the narrow piece is discarded, and the wider piece provides a racksection that can be welded or secured to others like it, with its teethin endwise register and congruent therewith, to produce a rack of thedesired width.

From the foregoing description, together with the accompanying drawings,it will be apparent to those skilled in the art that this inventionprovides a novel method of making racks by which the teeth of the rackscan be flame cut.

Those skilled in the art will also appreciatethat the invention can beembodied in forms other than as herein disclosed for purposes ofillustration.

The invention is defined by the following claims:

1. The method of making a rack, which is characterized by the steps of:

A. cutting through an elongated blank of rectangular cross section toproduce a kerf which extends from one wide side of the blank'to theother along its length and defines two laterally adjacent rack sectionswith equispaced meshing teeth thereon that are substantially identicalin shape and size;

B. laying one rack section against the other in such orientation thatthe teeth on the two sections project in the same direction, and anumber of teeth on one section are inexact register with teeth on theother section;

C. and securing the sections together in said orienta tion to form asingle rack having a width equal to twice the thicknessof the blank fromwhich the sections were cut. 1 2.'The method of making a rack accordingto claim 1, wherein said one section when layed against the other isdisplaced lengthwise of its original position a distance equal toone-half the spacing of its teeth.

3. The method of making a rack according to claim 1, wherein prior tothe'cutting of teeth in the blank, thin slices are flame cut from thenarrow longitudinal side edges of the blank.

4. The method of making a rack according to claim 1 wherein:

A. the teeth are cut by a flame passing throughthe blank from one wideside thereof, as a consequence of relative movement between the flameand the blank;

B. and said one section is layed against the other with while beingrestrained against thermal expansion the faces of the sectionscorresponding to said one in the opposite direction. wide side of theblank in contact with one another. 8. The method of making a rackaccording to claim 5. The method of making a rack according to claim 1,wherein:

4, wherein said one section when layed against the 5 A. the teeth arecut by a flame as a consequency of other is displaced lengthwise of itsoriginal position a relative movement between the flame and the distanceequal to one-half of the spacing of its teeth. blank;

6. The method of making a rack according to claim flame cutting iSCommenced at one end of the 5, wherein the flame cutting of teeth in theblank is blank and e ati e movement between the blank d d b a fl cuttingOperation i hi h hi 10 and the flame advances the latter toward theother slices are cut from the narrow longitudinal edges of the end ofthe blank; bl k C. and the blank is free to expand lengthwise toward 7.The method of making a rack according to claim saifl one end thereof asit is heated y the flame, 5wherein; while being restrained againstthermal expansion A. flame cutting of the teeth is commenced at one mthe PP direction end of the blank and relative motion between the methodof mak'ng rack accordmg to blank and the flame advances the later towardthe 8, wherein the flame is passed through the central zone other endofthe blank; of the blank at an equal average distance from the op- Band the blank is free to expand lengthwise toward Poslte longltudmalnarrow edges of the blanksaid one end thereof as it is heated by theflame,

1. The method of making a rack, which is characterized by the steps of:A. cutting through an elongated blank of rectangular cross section toproduce a kerf which extends from one wide side of the blank to theother along its length and defines two laterally adjacent rack sectionswith equispaced meshing teeth thereon that are substantially identicalin shape and size; B. laying one rack section against the other in suchorientation that the teeth on the two sections project in the samedirection, and a number of teeth on one section are in exact registerwith teeth on the other section; C. and securing the sections togetherin said orientation to form a single rack having a width equal to twicethe thickness of the blank from which the sections were cut.
 2. Themethod of making a rack according to claim 1, wherein said one sectionwhen layed against the other is displaced lengthwise of its originalposition a distance equal to one-half the spacing of its teeth.
 3. Themethod of making a rack according to claim 1, wherein prior to thecutting of teeth in the blank, thin slices are flame cut from the narrowlongitudinal side edges of the blank.
 4. The method of making a rackaccording to claim 1, wherein: A. the teeth are cut by a flame passingthrough the blank from one wide side thereof, as a consequence ofrelative movement between the flame and the blank; B. and said onesection is layed against the other with the faces of the sectionscorresponding to said one wide side of the blank in contact with oneanother.
 5. The method of making a rack according to claim 4, whereinsaid one section when layed against the other is displaced lengthwise ofits original position a distance equal to one-half of the spacing of itsteeth.
 6. The method of making a rack according to claim 5, wherein theflame cutting of teeth in the blank is preceded by a flame cuttingoperation in which thin slices are cut from the narrow longitudinaledges of the blank.
 7. The method of making a rack according to claim 5,wherein: A. flame cutting of the teeth is commenced at one end of theblank and relative motion between the blank and the flame advances thelater toward the other end of the blank; B. and the blank is free toexpand lengthwise toward said one end thereof as it is heated by theflame, while being restrained against thermal expansion in the oppositedirection.
 8. The method of making a rack according to claim 1, wherein:A. the teeth are cut by a flame as a consequency of relative movementbetween the flame and the blank; B. flame cutting is commenced at oneend of the blank and relative movement between the blank and the flameadvances the latter towArd the other end of the blank; C. and the blankis free to expand lengthwise toward said one end thereof as it is heatedby the flame, while being restrained against thermal expansion in theopposite direction.
 9. The method of making a rack according to claim 8,wherein the flame is passed through the central zone of the blank at anequal average distance from the opposite longitudinal narrow edges ofthe blank.